The present invention relates to electronically controlled glassware forming machines and, in particular, to a power failure detection system for use in such an electronic controller.
In general, the individual section glassware forming machine (IS machine) is well known in the art. The IS glassware forming machine comprises a plurality of, typically either, ten, or twelve, "individual sections". Each individual section includes all of the necessary elements for forming rigid glassware from a gob of molten glass. The individual sections of the glass forming machine typically cooperate with a "gob distributor" mechanism, which sequentially provides gobs of glass to the respective individual sections on a periodic basis. The individual sections of the machine also cooperate with a common conveyor system which is utilized to transport the rigid glassware to an annealing lehr. A "stacker" for arranging the glassware on the conveyor and ware inspection apparatus are typically disposed to operate on the glassware as it travels on the conveyor.
The respective individual elements of a section are operated in a cyclical timed relation, in synchronism with the gob distributor, to form the rigid glassware from the gob. The individual elements are typically driven by pneumatic pressure, selectively applied to the elements through a valve block associated with the section. Historically, the valve block cooperated with a mechanical controller in the form of a rotary drum, bearing respective cams corresponding to each functional element operation. The cams on the drum open or close cooperating mechanical valves (e.g. tappet valves) in timed sequence as the drum rotates. The relative dispositions of the cam about the perimeter of the drum control the timed sequence of operation of the individual section elements. A glassware forming machine utilizing a mechanical drum controller is described in U.S. Pat. No. 1,911,119 issued to Ingle in June, 1933.
More recently, electronic controllers and valve blocks have been utilized to effect the timed operation of the elements to form the rigid glassware. The first such electronic controller is described in U.S. Pat. No. 3,762,907 issued Oct. 2, 1973 to Quinn and Kwiatkowski, assigned to the common assignee herewith. The basic electronic controller now typically used in the industry is described in U.S. Pat. No. 3,969,703 issed to Kwiatkowski and Wood on July 13, 1976 and reissued as U.S. Pat. RE No. 29,642 on May 23, 2978. In general, the electronic controller includes a memory having locations corresponding to each section element operation. The memory location is loaded with, among other things, the point in the machine cycle when the operation is to be effected. (The machine cycle is typically thought of as being divided into 360 degrees, holding over the terminology that developed from the mechanical drum controller.) The stored cycle values are sequentially compared with indicia of the actual machine cycle position. Upon a favorable comparison, a signal is generated to an appropriate driver, which in turn operates on a solenoid valve.
As described in more detail in the above mentioned patent to Quinn and Kwiatkowski, U.S. Pat. No. 3,762,907, the IS section typically includes a delivery mechanism such as a scoop, trough and deflector for receiving the molten gob of glass from the gob distributor and depositing the gob through a funnel into a blank mold. A "settle blow" step is then effected whereby a baffle is positioned over the funnel and air is discharged into the blank mold through the baffle to force molten glass into a neck ring mechanism (for forming the mount of the glassware and any threads thereon). The neck ring mechanism includes a plunger which forms a small pocket in the gob. A counter blow step is then effected whereby the funnel is removed, the baffle moved against the top of the blank mold, the plunger retracted, and air introduced into the depression left in the glass by the plunger. The counter blow air causes the glass to fill the blank, forming what is known as a parison. The parison is then transferred to a blow mold on the other side of the machine. The counter blow step generates a cold skin on the parison to provide sufficient rigidity for the transfer. The blank mold opens, and a typical transfer mechanism, generally known as the invert arm, removes the parison from between the open halves of the blank mold and places it between the closing halves of a blow mold, supported in an upright position by the neck ring. The parison is then reheated (typically by the confined heat of the interior of the parison itself) and again becomes malleable. A final blow step is then effected whereby a blow head is positioned over the blow mold and blow air is forced into the soft parison, causing it to assume the shape of the blow mold. Heat is absorbed by the mold walls, cooling the glass to a point where it is sufficiently rigid to permit handling. The halves of the blow mold are then opened and a take-out mechanism grasps the ware at the neck thereof and transports it to a dead plate. After a predetermined cooling period, a push out arm moves the ware onto the conveyor.
Two problems that have plagued the glassware industry have been establishing initial synchronization between the gob distributor and the individual section and ensuring that molten glass does not harden on the machine elements if the machine operation is halted for some reason. More specifically, the machine elements of the section must be arranged in a predetermined initial state in order for the proper synchronized sequence of operations to be effected. However, when the machine is stopped on an emergency basis, the elements are typically not in the predetermined initial positions. In addition, even when the machine is stopped with the respective elements in a predetermined position, the elements are often manually moved by an operator during maintenance or the like. Moreover, molten glass is often still on or within the elements when the stop is effected. If glass is retained and hardens in an element, (particularly the molds), it typically must be chipped out, often with damage to the element. Such a chipping operation is exceedingly costly in terms of machine down time. Thus, it is necessary that provisions be made to facilitate the clearing of molten glass from the respective machine elements when machine operation is halted. This is particularly true where an electronic controller is used, rendering the machine more susceptible to power outages.
The problems associated with stopping and starting an IS machine are addressed in the above mentioned U.S. Pat. No. 3,762,907 to Quinn et al. As described in Quinn et al, a predetermined sequence of steps is performed without interruption before normal operation of the machine (i.e., actual formation of glassware) is begun. Similarly, a "programmed stop" is described whereby respective groups of elements are inhibited. For example, first, the "scoop on" function is inhibited, preventing further delivery of molten glass to the section. When the machine operation reaches the point in the machine cycle when the scoop on operation would normally be effected, various other functions such as "blank closed", "thimble on", "funnel on", "plunger on", "baffle on", "crack blank on", and "settle blow on" are inhibited. When the machine thereafter reaches the point where the "invert on" step would normally be effected, various other functions are inhibited: "neck ring off", "blow head on", "revert on", "final blow on", "mold close on", "take out arm on" , and "puff air on". Similarly, when the machine cycle again reaches the point where the "scoop on" operation would normally be effected, another group of functions is inhibited: "invert on", "bottom plate up on", and "button plate down on", "blank open on", "mold open on", and "counter blow on".
Thereafter, when the machine cycle reaches the point where the "invert on" operation would normally be effected, power is removed from all of the solenoid valves. Such a sequence of operation ensures that no molten glass is left in the section when it is stopped.
It was also recognized, in the Quinn and Kwiatkowski patent, that emergency circumstances can arise which do not provide time for running through a programmed sequence of steps before halting machine operation. Accordingly, an "emergency stop" was provided whereby power was removed from all of the solenoid valves so that the valves would assume respective normally opened or normally closed positions. A normally opened or normally closed valve was association with a particular element to facilitate removal of molten glass from the machine elements. For example, when power was removed from the associated solenoid, the respective molds would open, thus allowing the operator access to remove molten glass from the molds.
Programmed start, programmed stop, and emergency stop provisions are also described in the U.S. Pat. No. 3,969,703 Kwiatkowski and Wood patent.
In addition, systems have been proposed wherein the operating program, control program, and timing data are stored in a supervisory computer associated with a plurality of individual section computers. The control program and job histories for forming a particular glassware are stored in the supervisory computer and are selectively loaded into the individual section computers. The individual section computers then control the glassware formation. At predetermined intervals, the supervisory computer reads the current timing data from each of the individual section computers and stores the data in a non-volatile memory. Upon restoration of power after a power failure, the data is reloaded into the individual section computers. Loss of data and consequent down time are thus prevented. Such a system is described in U.S. Pat. No. 4,152,134 issued May 1, 1974 to Dowling et al. However, this type of a system does not address the problem of the retention of molten glass in the respective machine elements.